In the field of surgical tracking technology, electromagnetic (EM) tracking technology provides the ability to track very tiny sensors which can be integrated in medical instruments. Thus, even very small instruments such as for example catheters can be tracked inside a patient's body into which they have been introduced. However, the number of sensors which can be placed in the instrument is very limited. The number of channels an EM tracking system can track simultaneously is restricted, as is the space available for placing the sensors and their cabling in the instrument. For these reasons, it is typically the case that only a few parts of the instrument to be tracked are provided with a tracking sensor. One tracking sensor is for example placed in the tip of a catheter, such that only the position of the tip of the catheter can be tracked. The shape of the catheter remains undisclosed to the user.
U.S. Pat. Pub. No. 2012/0136626 to Mucha teaches a system and method for determining the shape of a surgical instrument such as a catheter. However, the system taught there requires the use of a plurality of sensors disposed along the length of a working portion of the catheter. This unfortunately renders the catheter design somewhat thicker than standard non-trackable catheters having otherwise equivalent medical characteristics, and somewhat heavier than standard non-trackable catheters having otherwise equivalent medical characteristics.
It is an object of the example embodiments of the claimed invention to provide a solution to the aforementioned problems. In particular, the example embodiments aim to enable the shape of an instrument, in particular the overall shape of an instrument having a limited number of tracking sensors, in particular only one tracking sensor, to be determined. It is another object of the example embodiments of the claimed invention to provide a corresponding instrument having a limited number of tracking sensors, in particular only one tracking sensor, wherein the shape of at least part of the instrument but in particular the overall shape of the instrument can be determined by tracking the available tracking sensors.
In particular, the example embodiments, replacing all of the tracking sensors except the one at the tip with a, for example, bending stress sensor helps in providing a slimmer and leaner trackable catheter.
In general, therefore, and in accordance with the example embodiments, a method is provided for determining the shape of a surgical instrument having a deformable body. The method of the example embodiment described herein includes steps comprising providing an elasticity model of an associated surgical instrument, and defining at least one parameter which influences the shape of the associated instrument. The method of the example embodiment further determines the spatial position and/or orientation of at least one tracking sensor of the surgical instrument, and determines the value of the at least one parameter. The method of the example embodiment still further calculates the position and/or orientation of at least one part of the associated surgical instrument using an elasticity model based on the determined value of the at least one parameter and the determined spatial position and/or orientation of the at least one tracking sensor.